The present invention relates to a system and method for sensing the angular position of a rotatable member. The present invention also relates to a rotatable member for use with a system and method for sensing the angular position of the rotatable member.
Many different types of rotatable members are used in automobiles and in other devices. Examples of rotatable devices include, but are not limited to, gears, bearings, shafts, tires, rotors, is hubs, and wheels. There are many instances where it is desirable to determine the angular position of these and other types of rotatable members. In automotive applications, it is desirable to sense the angular position of a gear, for instance, in the engine and drive train for startup and engine operation.
Typically, to sense the angular position of a toothed gear, at least one tooth is removed or shortened relative to the other teeth, and a magnetic sensor is provided to detect the absence of the tooth or the presence of a smaller tooth, as the case may be. Examples of such methods and apparatuses are shown in U.S. Pat. Nos. 4,797,827, 4,687,952, 4,152,655 and 5,497,748.
These types of gears which have a missing tooth or a shortened tooth have many shortcomings. For instance, gears that have a missing tooth or a shortened tooth are more susceptible to stresses, breakage, wear and noise relative to gears that do not have a missing or shortened tooth. As such, it would be desirable to provide a method and system for sensing the angular position of a rotatable member which does not rely on a missing tooth or a shortened tooth to determine the angular position of the rotatable member.
It is an object of the present invention to provide a method and system for sensing the angular position of a rotatable member which does not rely on a missing tooth or a shortened tooth to determine the angular position of the rotatable member.
It is another object of the present invention to provide a rotatable member which does not have any missing or shortened teeth and whose angular position is readily determinable.
The above and other objects of the present invention are met by providing a system and method for sensing the angular position of a rotatable member. The system and method employ the use of a composite rotatable member comprising a solidifiable material and a magnetically attractable particulate material. The rotatable member has a major body portion and at least one magnetically detectable reference point. The reference point has a first magnetic property and the major body portion has a second magnetic property, different from the first magnetic property. A magnetic property sensor is fixed relative to the rotatable member. The sensor is able to detect the passage of the reference point within the rotatable member. The sensor produces a signal in response to the passage of the reference point. A central processing unit is provided for determining the angular position of the rotatable member in response to the signal generated by the sensor.